The present disclosure relates to an in-line mixing apparatus which is especially suitable for use in processes for extracting iodine from an aqueous solution containing soluble iodine ions such as iodide. Also included are various processes for extracting iodine from aqueous solutions using such an apparatus.
Elemental iodine (I2) is a valuable chemical having many industrial and medicinal applications. There is an increasing demand for iodine and its major derivatives, iodide salts. The consumption of iodine and iodide salts is distributed among several industrial applications, such as catalysts, animal feed additives, stabilizers for nylon resins, inks and colorants, pharmaceuticals, disinfectants, film, and other uses. A great deal of attention is therefore focused on the recovery of iodine from various sources, either as a primary product or as a by-product of other industrial processes.
Iodine is generally recovered by physical and/or chemical manipulation of an aqueous solution containing soluble iodine ions like iodide (I1−) or iodate (IO31−). Exemplary solutions include leaching solutions used in nitrate extraction and brine solutions. The term “brine” in this context includes industrial and naturally occurring salt solutions containing iodine in various salt forms. Exemplary brines are seawater and natural brines such as those associated with petroleum deposits and with solution mining of salt domes.
It has been known to extract iodine from aqueous solutions containing iodide, such as brine, by acidification with a mineral acid and thereafter adding an oxidant such as chlorine to liberate the iodine. This extraction is described in U.S. Pat. No. 3,346,331 to Nakamura. The reference further discloses the use of an anion-exchange resin to adsorb iodine from brine. Nakamura also discloses alternating passage over the anion-exchange resin of the iodide-containing solution, which has chlorine added to it, with the iodide-containing solution without the added chlorine. This cycle repeats until the resin is saturated. Finally the resin is treated with sodium hydroxide solution followed by a sodium chloride solution to elute iodine from the resin in the form of iodide (I1−) and iodate (IO31−). The iodine in the combined eluents is recovered by adding mineral acid to convert iodide and iodate to iodine, which will crystallize out.
U.S. Pat. No. 4,131,645 to Keblys discloses a system of iodine recovery similar to that of Nakamura. Keblys discloses passing brine through an anion-exchange resin without acidification or oxidation, whereby the resin adsorbs iodide from the brine. The adsorbed iodide is then oxidized by passing a separately prepared aqueous iodate solution through the resin. The aqueous iodate solution is acidified with hydrochloric acid to a pH of about 1-4 before use. Keblys discloses repeating cycles of passing brine then passing acidified aqueous iodate solution through the resin until the resin is saturated.
It would be desirable to develop additional methods to increase the amount or rate of iodine extraction, and to develop additional devices or apparatuses for implementing such methods.